is based on a statistical noise model and can accommodate a sophisticated system response model, is a widely accepted solution.The objective of this work was to preserve or improve reconstructed image quality at either the same or reduced x ray radiation exposure using statistical reconstruction for a newly constructed high-resolution small animal SPECT/CT dual-modality system. The reconstruction performance at different radiation exposure levels was assessed. This paper reports only our work on the CT aspects of the system. The overall system development and performance are reported in a separate paper [1].
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MATERIALS AND METHODSAbstract-We developed a statistical iterative CT ima g e reconstruction software for a newly constructed hi g h-resolution small animal SPECT/CT dual-modality system, and assessed its performance at different radiation exposure levels. The objective of this work was to preserve or improve reconstructed ima g e quality at either the same or reduced animal x-ray radiation exposure. The SPECT/CT system used a sin g le detector for both the CT and SPECT modalities that consists of a micro-columnar CsI(TI) phosphor, a li g ht ima g e intensifier (LII) and a CCD sensor. The CT reconstruction software was based on the ordered-subset-convex (OSC) al g orithm, and the system matrix was calculated throu g h a ray-driven approach. A self-calibration method was implemented to calculate the offset of the axis of rotation (AOR), an important g eometry parameter of the system. An endovascular stent was imaged to evaluate the hi g h resolution performance of the statistical reconstructed ima g e. A sacrificed mouse was scanned at different exposure levels to assess the effect of statistical noise on the ima g e. The mouse studies were reconstructed with both the statistical reconstruction software and a filtered back-p rojection (FBP) p ro g ram. The ima g es were assessed and com p ared by contrast to noise ratio (CNR) in the re g ion of interest. The ima g es yielded by the statistical reconstruction software were artifact free and show su p erior noise p erformance to those from FBP reconstruction at different radiation exposure levels. The statistical reconstructed ima g es with reduced exposure showed obviously hi g her ima g e quality than those from FBP reconstruction at full exposure.
